Preparations for nanoparticle metal and metal oxide hydrosols are known. The myriad methods for preparing these particles include, but are not limited to: (1) the synthesis of colloidal dispersions of various transition metals (Pt, Pd, Ir, Rh, Os, Au, Ag, Fe, Co, and the like) in aqueous media, stabilized by added polymers as protective colloids; (2) the synthesis of ultrasmall metal oxide particles by the combination of water and metal chlorides, hydroxides, or acetates, in aqueous media; (3) the synthesis of Ag nanoparticles by the reduction of Ag+ in aqueous media; (4) the formation of colloidal silver and gold in aqueous media by ultrasonic radiation; (5) the formation of colloidal gold in aqueous media by the reduction of a gold salt; and (6) the formation of colloidal platinum and palladium in aqueous media by synthetic routes analogous to those for preparing gold colloids. The fabrication of large metal cluster complexes with various stoichiometries and ligands (e.g. M.sub.55 L.sub.12 Cl.sub.x, M=Rh, Ru, Pt, Au; L=PR.sub.3, AsR.sub.3 ; x=6, 20; R=Ph, t-Bu) is also known.
Nanometer-scale crystallites of various metals and non-metals have received a great deal of attention in the past decade. For such crystallites, the electronic, thermodynamic, and chemical properties depend sensitively on size, shape, and surface composition; therefore, these materials have been marked for a number of technological applications ranging from chemical catalysis, photoelectronics, film growth seeding, electronic materials, reprography, xerography, electron microscopy, and others. A major challenge to this field in general and a great barrier to actualizing such applications of these novel particles is the complete control over particle size, morphology, and surface structure. The preparation and isolation of crystallites characterized by well-defined surface compositions, narrow size distributions, and uniform shape is paramount to their success as applied materials. In addition, most of these applications require that the particles be dispersible into some solvent, polymer, or other matrix as a monodisperse (non-aggregated) colloid, and that they exhibit various chemical and thermal stabilities. Metal particles involved in these various technologies include ferromagnetic materials (e.g. Fe.sub.2 O.sub.3, Co), noble metals (Pd, Pt), coinage metals (Au, Ag), alloys of these metals (e.g. Co.sub.x Au.sub.y), oxides of these metals (e.g. Ag.sub.2 O), and others.
To date, there are only a few reports concerning the preparation of organically-functionalized metal nanoparticles. However, the products synthesized in these reports are marred by some or all of the following characteristics: 1) the resulting materials are x-ray amorphous (non-crystalline); 2) the resulting materials have poor surface compositions; 3) the resulting materials have poor solubility in aqueous and organic media; and 4) the resulting materials have broad relative size distributions (mean diameter .+-.50%). For example, organically-functionalized gold nanocrystals limited to certain "average" sizes, characterized by broad size distributions, and which are not soluble in aqueous media have been disclosed.